Helo, new M92 user here. I am an e-reader newbie so I have a probably very stupid question: when using Onyx Boox readers for the first time is it better to fully charge them (or at least charge them as much as possible, in the case of the M92) or is it better to use them until the battery completely runs out of juice? As far as I know, the second option is the best one with mobile phones but I don't know how things work in the case of e-book readers... Tahnk you!!

That's a hold over from days gone by. Batteries nowadays are Lithium-Ion (or more rarely Nickel–Metal Hydride) not Nickel-Cadmium which had the memory effect issue. It doesn't matter any more. Charge and use as you see fit.

What is still true is that no matter the tech a battery will lose capacity over time but there's little you can do about it unless you want to put it in a freezer (half charged). Just forget about it and charge when you have the opportunity.

My device charges up to 100% in a very short time, so hopefully it's not a built-in problem (however just as predicted by Murphy's law my USB cable does not seem to work since my PC does not recognise the device as a removable disk... great!)

EDIT: Now that's weird... the device showed battery charged 100% but now, with the device still plugged in shows battery charge 98%... so I suppose my device too has the same precision/reliability issue

My device charges up to 100% in a very short time, so hopefully it's not a built-in problem (however just as predicted by Murphy's law my USB cable does not seem to work since my PC does not recognise the device as a removable disk... great!)

EDIT: Now that's weird... the device showed battery charged 100% but now, with the device still plugged in shows battery charge 98%... so I suppose my device too has the same precision/reliability issue

It is not weird at all. Chargers for lithium batteries stop charging when the battery is full as part of a mostly successful effort to prevent a fiery explosion. Charging does not resume until the battery has discharged a little. Different manufacturers make different choices as to when to resume charging.

It is not weird at all. Chargers for lithium batteries stop charging when the battery is full as part of a mostly successful effort to prevent a fiery explosion. Charging does not resume until the battery has discharged a little. Different manufacturers make different choices as to when to resume charging.

Well good to know then! Thank you for your explanation, it turns out that although I considered myself very moderately nerd (erg, I use Linux - but don't know how to do anything from Terminal, my brother does everything for me !!!) I'm way more ignorant than I thought